Formatted vs. unformatted IO of files such as WF1.mmn, WF1.uHu, WF1.mmn0,...
Wannier90 allows us to specify whether files such as WF1.mmn and WF1.amn and WF.uHu are read in as formatted or unformatted files.
Using unformatted files instead of formatted files saves considerable disk space.
When the key "unformatted" is present in the jobList in the wannier section of the inp.xml file, all big matrices such as WF1.mmn are written out as unformatted files.
Instead of using the "unformatted" key you may specify the format for each matrix separately. For example, using the keys matrixmmn=2, matrixamn=1 will write the WF1.mmn as an unformatted file, but WF1.amn as a formatted file. Using the keys matrixmmn=1, matrixamn=1, matrixuhu=2, mmn0=2 will write the WF1.mmn and the WF1.amn as formatted files, but the WF1.uHu and WF1.mmn0 as unformatted files. When you specify in this way the format separately for all files, you should not specify the unformatted key, because when the unformatted key is specified, all big matrices are written as unformatted files.